SAN ANTONIO -- Lack of space and services for the more than 500,000 people expected to attend a papal mass here in September may result in "people dying like flies," warned the city's top health officer, who resigned in protest one month before her planned date for leaving.

"Unless proper attention is paid to the need for limiting the size of the crowd and providing an adequate water supply, I'm concerned we may have hundreds of people dying and thousands of casualties," Dr. Katharine Rathbun, director of the San Antonio Metropolitan Health District, said Monday.

"The reason I'm resigning is that I think at this point the only thing that many of us can do is say to people, 'Don't come and, particularly, don't bring children and don't bring elderly or infirm people, because they are the most likely to die from heat or in a stampede of a crowd,' " she said.

Other city officials and spokesmen for the city archdiocese said adequate steps were being taken to handle the crowds expected for the Sept. 13 visit of Pope John Paul II and a mass at a 144-acre site just west of the city.